- #1

- 37

- 0

## Homework Statement

Two boxes are attached to opposite ends of a rope passing over a frictionless pulley as shown below. The mass of Box A is 15kg and the mass of box B is 12kg. The system is originally at rest with the bottom of box A at a height of o.85m above the floor. When the system is released, the boxes will move. Use conservation of energy to determine the speed with which Box A will contact the floor.

## Homework Equations

Eg=mgΔh

Ek= 1/2 mv^2/2

ƩFy=may

## The Attempt at a Solution

I started off by drawing free body diagrams of each mass, one at rest, and one in motion.

For mass A:

at rest,

ƩFy=0

Ft+Eg=0

Ft= Eg

= mgΔh

=(15kg)(9.8m/s^2)(0.85m)

Ft=125N

in motion,

ƩFy= may

Fg(A)-Ft= m(A)ay

For mass B:

at rest,

ƩFy=0

Fn-mg=0

Fn=mg

=(12kg)(9.8m/s^2)

Fn=117.6N

in motion,

ƩFy=may

Ft-Fg(B)= m(B)ay

I'm not sure if my original statement of Ft=Eg is accurate... and from this point on I don't know where to go.